The study tracked 15,297 charter school students at 64 schools from grades 3-8. On average, students in charter schools ended the year having made the equivalent of 1.5 more months of learning gains in both reading and math than their traditional public school counterparts did. Students in charter schools in Indianapolis ended the year ahead of their traditional public school counterparts by two months in reading and three months in math.

Charter students and the control group were matched by demographic and performance data (gender, race/ethnicity, special education status, English language proficiency, free-or-reduced lunch participation, grade level, and prior test scores on state achievement tests).

In Indiana, 58 percent of charter students are black, compared to 11 percent of the state’s students. Eleven percent of charter students are in special education compared to 15 percent in traditional public schools.

In a wrap-up on education research in 2012, Matthew Di Carlo notes that CREDO’s research on charter gains in Indiana and New Jersey show most of the progress comes in big cities, Indianapolis and Newark. By contrast, rural charter students tend to underperform similar students.

One contentious variation on this question is whether charter schools “cream” higher-performing students, and/or “push out” lower-performing students, in order to boost their results. Yet another Mathematica supplement to their 2010 report examining around 20 KIPP middle schools was released, addressing criticisms that KIPP admits students with comparatively high achievement levels, and that the students who leave are lower-performing than those who stay. This report found little evidence to support either claim (also take a look at our post on attrition and charters).

An another analysis, presented in a conference paper, “found that low-performing students in a large anonymous district did not exit charters at a discernibly higher rate than their counterparts in regular public schools,” DiCarlo adds.

On the flip side of the entry/exit equation, this working paper found that students who won charter school lotteries (but had not yet attended the charter) saw immediate “benefits” in the form of reduced truancy rates, an interesting demonstration of the importance of student motivation.

Di Carlo has more on the research this year on charter management organizations, merit pay and teacher evaluations using value-added and growth measures.